A recent innovation in this field is the discovery of superconductivity in cuprate perovskites that show critical temperatures of the order of hundred degree's Kelvin. However this class of ceramic superconductors has a limited industrial application because these materials are fragile, they are difficult to shape and it is difficult to keep under control the oxygen content. These difficulties generate limits for the industrial applications of superconducting electronic devices using these ceramic materials.
Another difficulty for the advances in this field is due to the lack of a theory that explains the superconductivity at high temperature in these materials, therefore the progress in these materials advances by empirical approaches.
Superconducting cuprate perovskites have been described as natural superlattices of first superconducting CuO.sub.2 layers with a two dimensional electronic structure, sandwiched by second blocking layers made of insulators, or metals with lower T.sub.c, stacked in the c axis direction and similar artificial superlaltices have been synthesized (Physical Review Letters Vol 63, No. 9 August 1989, pages 1016-1019; J. -M. Triscone, M. G. Karkut, L. Antognazza, O. Brunner, .O slashed.. Fisher: "Y-Ba-Cu-O/Dy-Ba-Cu-O Superlattices: A First Step towards the Artificial Construction of High T.sub.c Superconductors") and it has been also discussed in a recent patent application (Toray Industries, European Patent Appication EPA 0 502 204 A1, International application number PCT/JP91/01255, International publication number WO 92/0514 (02.04.92 92/08)); and in some papers (Physica C, Vol. 190, ISSN 0921-4534 Nos. 1/2 Decmber 1991, pages 22-26; Qi Li, T. Venkatesan and X. X. Xi: "Growth and superconducting properties of YBa.sub.2 Cu.sub.3 O.sub.7 -based superlattices"); (Physica C, Vol. 185-189, ISSN 0921-4534, Dec. 1, 1991, pages 1747-1748; M. Holcomb, J. P. Collman, and W. A. Little: "New phenomena in proximity effect tunneling of high T.sub.C superconducting cuprates"). Moreover also superconducting films of doped fullerene, such as K.sub.3 C.sub.60, can be made for the production of intricately layered microelectronic devices (Scientific American (Int. Edition) October 1991, USA, vol. 265, no. 4, ISSN 0036-8733, pages 32-41 R. F. Curl and R. E. Smalley "Fullerenes").